Recording thermometer



Sept. 27, 1938. M. o. SNEDXKER 2,131,573

RECORDING THERMOMETER Filed NOV. 9, 1936 l 1 I I I I I I Inz/ezfibr; Mariam fizzficidie i Patented Sept. 27, 1938 RECORDING THERMOIWETER Morton 0. Snediker, Chicago, Ill., assignor to The I Powers Regulator Company, Chicago, 111., a

corporation of Illinois Application November 9, 1936, Serial No. 109,926

2 Claims. (Cl. 234-72) My invention relates to recording instruments and particularly to novel compensating means for use in connection with recording thermometers. A construction similar to that herein described and claimed was first disclosed in my copending application Serial No. 33,649, filed July 29, 1935.

It is well known that volatile liquids expand on the application 01' heat in cumulative ratio; that is, the pressure developed on the application of heat is not in direct proportion to the temperature increase. This has necessitated the provision in the charts for recording thermometers, of circular division lines of gradual increasing width as higher temperatures are indicated (or recorded). Thus at a point near the center, the lines would be relatively closely spaced, making reading of the chart dimcult and the results inaccurate.

Numerous expedients have been adopted for compensating for the increasing pressure of the thermostatic liquid, but as far as I am aware, no mechanism has been proposed in which the same instrument is adapted for operation in connection with diflerent thermostatic liquids or in which the range as recorded on the chart might be changed. By range" I mean as follows:

Where the necessity for close indications is not essential, a chart may be used where the range between the circular division lines may include 25 degrees of temperature change; that is, 5 degrees between each of the light division lines. Obviously this does not provide for close regulation or indication. In other cases where close regulation is necessary, it may be found desirable to provide for only 5 degrees between the main division lines; that is, one degree for each of the intermediate division lines. The compensating mechanism here disclosed is so arranged that the same instrument may be used for either of the two extreme conditions, merely by adjustment of the compensating mechanism. This is an advantage, not only to the manufacturer, who may standardize his parts, but to the user, who may wish to change the instrument from one to the other condition. The mechanism also provides for accurate compensation in any of the different ranges.

My invention will be more readily understood by reference to the accompanying drawing; in which,

Fig. 1 is a front elevation of apparatus constructed in accordance with my invention; and,

Fig. 2 illustrates the same mechanism, with a change in a link used therein and a change of being such as to provide for the maximum range of movement.

In the drawing I have illustrated a part of the dial 10 of a recording thermometer, a shaft II and a chart clamp l2 being added as essential elements of a recording instrument. A chart l3 having main division lines l4 and intermediate lines I5 is shown in place. A pen arm I6 is provided which is mounted on a pivot I! having a crank IS, the pen arm operating in the usual manner. The crank is adjustable as to length, it being screw threaded through the sleeve that carries the pen arm pivot IT.

A bellows I9 is fixed to the instrument, the bellows being adapted to be influenced by pressure developed by a volatile liquid in a bulb, not shown, a. tube 20 providing communication between the bulb and bellows. The upper wall of the bellows is movable, the movement thereof being transmitted through a projection 2|. Pivoted to the projection is a range control bar 22, the pivot 23 thereof also providing a support for a gear sector 24 having an arcuate slot 25 therein. A set screw 26 serves to connect the bar 22 to the gear sector and to firmly hold those parts against movement, except when adjustment is to be made. A pinion 21, is carried on a headed shaft mounted on the bar, the pinion engaging the gear 24. A slot in the said head enables the use of a screw driver for turning the pinion and thereby effecting a very fine adjustment between the bar and the gear sector.

While I have shown a gear sector for the described purpose, yet the function of this part is merely that of an arm projecting substantially transversely of the line of movement of the bellows end wall. In the position of Fig. 1 the arm and bar constitute in effect a bell crank, while in the position of Fig. 2 the parts are arranged so that the bar is in effect a motion multiplying lever.

The fulcrum for the arm, which is the term that will be used in referring to the part 24, consists of a link 28 mounted on a fixed pivot 29 at one end and at the other end having a series of holes 30, preferably spaced A; inch apart. The sector or arm also has three or more holes 3|, preferably spaced inch apart. By the use of the connecting pin 310, it will be seen that by proper selection of the holes a very close adjustment may be secured, this being the means for bringing about the compensating action of the mechanism, and the adjustment serving to adapt the instrument to all of the ordinary volaposition of the actuating unit, the adjustment tile liquids that are used for regulating purposes. The of movement oi the pen arm is de termined the degree oi angular"'y oi the liar from a vertical position as shown in thin. I. and lay the length of the crank iii. In the posi tion of Fig. 1 an adjustable link connects the upper end of the bar to the crank it and will be seen that the upward hodily movement of the bellows is transmitted in a direct vertical line through the bar to the shortened crank iii. However, as the fulcrum point oi the arm li t, represented by the pin Sic, is hired, the am will not rise, but will rotate and thereby came the bar to swing to the right as viewed in i, thus tending to straighten out the line betwe the pivot and the end of the crank i8. insures the correct compensation for short range control with the parts disposed as shown.

However, if wide range control is desired, for example where each of the circles 95 represent one degree of temperature change, then the bar 22 is swung to the extreme position shown in 2 and a longer link 33 is provided to connect the end of the loar to the crank. Thus the bar 22,

' together with the arm 24 becomes a motion multtplying lever and for any unit of movement of the bellows, the movement of thepen arm is in shifted to the position si'iown Figure 2 creased. to the extent of the motion mnltiplica tion as between the pivot points 23 and The degree of multiplication is determined h-y the position of the pin Ma and the angular posi tion of the arm 22. I

in order to adapt the operating mechanism to the longer link 33, it is desirable to change the bodily position of the operating unit relative to the shaft ii that carries the pin arm. Consequently the unit which is supported on the bracket 5 and held in position against the hash plate 6 of the instrument by the screws in in strwnen. e combination of a thermo-responsive element "ring a movable part, a bar bodily movable wi ie part and pivoted thereon, an aim fixed to said bar and angularly adjustable the pivot of the bar, a link mounted at one end on fixed pivot and at the other end connected to the arm and providing a fulcrum point therefor, a pen arm shaft and a crank thereon, and a link connecting the crank to the free end of the bar.

3. In a recording instrument, the combination with a thermo-responsive element having a movable part, a bar pivoted on said part and bodily movable therewith, an arm projecting transversely of the line of movement of said part, said arm heing fixed to the bar with capacity for anguiar adjustment relative thereto, said arm being in the term of a gear sector and said bar carrying a pinion for engagement therewith, a link mounted on a fixed pivot at one end and at the other end connected to the free end of said arm and providing a iulcrum therefor, a pen arm ohaift and a crank thereon and a link connecting the cranit to the upper end of said bar.

MURTUN' 0. SNEDIKER. 

